[MacViews] Enable dragging a window by its caption/draggable areas.

ui/views/cocoa/bridged_native_widget.h

Index: ui/views/cocoa/bridged_native_widget.h
diff --git a/ui/views/cocoa/bridged_native_widget.h b/ui/views/cocoa/bridged_native_widget.h
index badda952339963177b0c5ded3ec992bb78f4d53e..77cf10c6869a750657d69363c19f2dc5173fd3f1 100644
--- a/ui/views/cocoa/bridged_native_widget.h
+++ b/ui/views/cocoa/bridged_native_widget.h
@@ -132,6 +132,12 @@ class VIEWS_EXPORT BridgedNativeWidget : public ui::LayerDelegate,
   // Called by the NSWindowDelegate when the window becomes or resigns key.
   void OnWindowKeyStatusChangedTo(bool is_key);
 
+  // Called when the application receives a mouse-down, but before the event

[tapted, 2015/05/22 04:03:12]

nit: start with "Called by the NSWindowDelegate". Maybe this should be some kind
of privateAPI that only the delegate can see... but ObjC doesn't play nice with
`friend` declarations.

[jackhou1, 2015/05/25 04:50:19]

Done.

+  // is processed by NSWindows. Returning true here will cause the event to be
+  // cancelled and reposted at the CGSessionEventTap level. This is used to
+  // determine whether a mouse-down should drag the window.
+  bool ShouldRepostPendingLeftMouseDown(NSPoint location_in_window);
+
   // Called by NativeWidgetMac when the window size constraints change.
   void OnSizeConstraintsChanged();
 
@@ -189,6 +195,10 @@ class VIEWS_EXPORT BridgedNativeWidget : public ui::LayerDelegate,
   // scale factor.
   void UpdateLayerProperties();
 
+  // Sets mouseDownCanMoveWindow on |bridged_view_| and triggers the NSWindow to
+  // update its draggable region.
+  void SetDraggable(bool draggable);
+
   // Overridden from CocoaMouseCaptureDelegate:
   void PostCapturedEvent(NSEvent* event) override;
   void OnMouseCaptureLost() override;